A rear axle of a vehicle is typically mounted on the frame by a leaf spring whose opposite ends are continually held to the frame by connectors and whose middle portion lies directly over the rear axle. The leaf spring is preferrably constructed so that under quiescent conditions its top is flat. When the spring is "reversely" curved, so that its top surface is convex, the ride is harsh. One way that has been used to avoid reverse bending is to place an air sleeve or air bag between the frame of the vehicle and the axle. However, this has been found to still result in a relatively harsh ride. An air sleeve would appear to be a good mechanism for helping to absorb shock in combination with the length of the leaf spring, but none of the systems known to applicant have produced a very smooth ride.
It may be noted that air sleeves have been proposed in the patent literature for use in conjunction with leaf springs to support one end of the leaf spring, with all of the load transmitted through the front portion of the leaf spring being transmitted through the air sleeve. In two patents of this type, U.S. Pat. No. 3,309,107 by Chieger (FIGS. 5 and 7) and U.S. Pat. No. 3,063,732 By Harbers, air bags or sleeves have been placed at the front of the leaf spring so all shock has been transmitted through the air bags. However, such air bags must be large so they are capable of transmitting large forces, since at least half of the weight supported by the adjacent vehicle tire must be transmitted through the air bag. Also, the air bag then does not avoid reverse spring curvature. An air sleeve assembly which enabled most of the shock to be transmitted through ordinary connectors, with a moderately low capacity air sleeve serving to supplement the leaf spring and prevent reverse curvature of the leaf spring, and which resulted in a very smooth ride, would be of considerable benefit.